This invention relates to a positive working radiation sensitive coating composition having high sensitivity to radiation such as electron beams, ion beams, X-rays, etc., particularly to a radiation sensitive coating composition suitable for forming a radiation sensitive resin film having good compatibility.
A process for producing semiconductor devices using a radiation sensitive composition comprising an alkali soluble novolak resin and poly(2-methylpentene-1-sulfone) is disclosed in Japanese Patent Appln Kokai (Laid-Open) No. 153578/79 but only a mixed solvent of methoxyethyl acetate and cyclohexane is disclosed therein as a solvent for such a composition.
In general, compatibility between poly(2-methylpentene-1-sulfone) and novolak resins is not so good. Thus, when a solution of the two is coated on a substrate and dried to form a coating film, it is found that phase separation of the two readily takes place and a coating film with homogeneous quality cannot be obtained. Since the resulting coating film is a positive type or positive working wherein portions exposed to radiation are solubilized to a developer, when the coating film is unhomogeneous, the exposed portions and unexposed portions only show a slight difference in solubilities to the developer. Therefore, the formation of homogeneous coating film from the above-mentioned two resin componenets has long been desired.